1. Field of the Invention
The present invention relates to a self-regulating valve assembly for use with a fluid exchange system for matching fluid in-flow and out-flow from an accessed hydraulic circulation circuit, more particularly such as an automatic transmission fluid cooling circuit.
2. Background of the Invention
Devices and methods of use thereof for exchanging used automatic transmission fluid (ATF) with fresh ATF from an automotive transmission have recently been widely accepted. Such devices may access the fluid cooling circuit of an automobile and introduce fresh fluid at a predetermined flow rate while simultaneously extracting a similar predetermined flow rate of used fluid from the cooling circuit. Earlier advances in the art, for example, include U.S. Pat. Nos. 5,318,080 and 5,472,064, both to Viken, and both herein incorporated by reference. The importance of balancing fluid introduction and extraction is also widely recognize. Accordingly, it is desirable to maintain approximate parity between the introduction of fresh fluid into an automatic transmission and the extraction of used fluid out of the transmission in a fluid exchange apparatus while performing an exchange of the transmission's used fluid for fresh fluid.
A need has developed for devices and methods for use thereof for exchanging used hydraulic fluid with fresh hydraulic fluid in a closed or open loop hydraulic systems. Such devices would desirably access a hydraulic circuit and introduce fresh hydraulic fluid at a predetermined flow rate while simultaneously extracting a similar predetermined flow rate of used hydraulic fluid from the access circuit.
Many prior art devices have relied on operator or other intervention to monitor and control an external pump which introduces fresh fluid at a balanced rate in an exchange system. Operator control of the fluid pump is an obvious limitation in that exchange performance relies on the relative skill of operator.
Finally, many machines and methodologies have recently been developed for ATF exchanges of automobiles. However, the devices and methods have typically been relatively complex in design and application. A need exists for a simple, fail-safe automatic transmission fluid exchange device.